1. Field of the Invention
The present invention relates to an electronic device including a plurality of flip-chip mounted electronic components.
2. Description of the Related Art
Flip-chip mounting is an example of a mounting method for decreasing the size and height of an electronic device including a plurality of functional elements and electronic components.
FIG. 9 is a cross-sectional view of an electronic device disclosed in Japanese Unexamined Patent Application Publication No. 2001-257236. FIG. 9 discloses an electronic device including two flip-chip mounted surface acoustic wave elements arranged in a single package form. The electronic device shown in FIG. 9 is a surface-mounted dual filter including a substantially cavity-shaped package 601, a cap plate 602, and two surface acoustic wave elements 611 and 612 mounted by flip-chip bonding. Spaces 641 and 642, in which interdigital transducer (IDT) electrodes 632 configuring the surface acoustic wave elements 611 and 612 are arranged, are provided by bumps 621 and 622. The package 601 and the cap plate 602 are bonded to each other by a brazing material 603 made of solder with a high-melting point, and hence the inside of the package 601 is hermetically sealed.
A method of decreasing the size of a flip-chip mounted electronic device may be decreasing the distance between two electronic components. However, if the distance between the two electronic components to be mounted is decreased, when the second electronic component is mounted, for example, the mounting tool may interfere with the mounted first electronic component, and the first electronic component may be physically damaged, possibly degrading characteristics and reliability. Owing to this, Japanese Unexamined Patent Application Publication No. 2001-257236 suggests a method of preventing interference with the mounting tool by setting the thickness of the surface acoustic wave element 611, which is mounted later, to be larger than the surface acoustic wave element 612, which is mounted first. To be specific, a thickness tx1 of the surface acoustic wave element 611 is larger than a thickness tx2 of the surface acoustic wave element 612, and the height of the bump 622 bonded to the surface acoustic wave element 612 is equivalent to the height of the bump 621 bonded to the surface acoustic wave element 611. Hence, a step is generated between the upper surfaces of the two surface acoustic wave elements 611 and 612 by the difference between the thicknesses of the two surface acoustic wave elements 611 and 612.
However, if a difference in thickness is provided among a plurality of electronic components, such as the electronic device disclosed in Japanese Unexamined Patent Application Publication No. 2001-257236, when the plurality of electronic components are sealed with a sealing member such as resin in a later step, an inclination is generated at the upper surface at the sealing member side of the sealed electronic device. If the inclination at the upper surface is large, the following problems may occur in manufacturing mounting steps. For example, (1) in a dicing step (a cutting step with a dicing machine) after sealing, a defective product may be generated due to non-uniform cutting, (2) when the electronic device is picked up using the upper surface by sucking etc., the upper surface cannot be picked up, and (3) a mark stamped on the upper surface cannot be recognized.